1. Field of the Invention
The present invention relates to a composition for post-implant, etch/post-etch and post-ash related processes in the semiconductor/IC production field. More specifically, the present invention relates to formulations capable of tuning the etch rates of titanium nitride (TiN) and tungsten (W) with the purpose of removing TiN and organic and/or inorganic residues from a surface.
2. Description of the Prior Arts
Integrated circuits (IC) are made up of millions of active devices formed in or on a silicon substrate. The active devices, which are initially isolated from one another, are united to form functional circuits and components. The devices are interconnected through the use of well-known multilevel interconnections. Interconnection structures normally have a first layer of metallization, an interconnection layer, a second level of metallization, and in recent years a third and subsequent level of metallization.
In the semiconductor/IC production field, the post-etch residues (PERs) are usually removed by means of wet cleaning processes. Solutions comprising complexing agents and water can be used here. Moreover, selective etching of different layers, within the microelectronic structure, is considered a critical and crucial step in the IC fabrication process. In the first layer of metallization, which includes a tungsten plug (W-plug), TiN and low-k dielectric material, it is desired to be able to etch TiN at such a rate, that the W-plug is not significantly damaged. In subsequent layers of metallization, which mainly contain copper (Cu-plug), it is desired to be able to etch the TiN at such a rate, that the copper plug is not significantly damaged. Depending on the individual thicknesses of the TiN and metal layers, which depend greatly on the integration scheme used, this requires solutions that are capable of tuning the etch rates of TiN and metal (W or Cu).
It should be understood, that the presence of oxidants in the formulations, such as hydrogen peroxide, can be necessary to achieve a sufficiently high etching rate of TiN. However, an undesired effect is that the etch rate for tungsten, copper and related metals increases as well by the addition of an oxidant such as hydrogen peroxide. Thus, there is a need to find suitable additives that allow tuning of the etch rates of TiN and W whilst being capable of removing organic and/or inorganic residues (e.g. F-containing) from the wafer surface.
U.S. Pat. No. 7,919,445 relates to a novel solution for the removal of post-etch residues. Imidazoline compounds as corrosion inhibitors are preferably added for the treatment of wafer surfaces having, for example, tungsten and aluminum metallization.
WO03060045 relates to aqueous compositions used to remove photoresist, etch and ash residue and contaminants from semiconductor substrates. A single corrosion inhibitor compound or mixture of corrosion inhibitors such as for example benzotriazole, benzoic acid, malonic acid, gallic acid, catechol, ammonium malonate, can be used in the stripping and cleaning compositions. WO03060045 does not use oxidants for the etching of TiN, nor does it discuss the protection of W.
WO06138505 relates to dense fluid compositions, e.g., supercritical fluid compositions, useful for the removal of hardened photoresist, post-etch residue and/or bottom anti-reflective coating layers from the surface of microelectronic devices. However, at least one fluoride source is contained in said fluid compositions, which would damage low-k dielectric materials. WO06138505 does not concern the etching of TiN and the protection of W, either.
EP1552342B1 is concerned with selectively removing etching residues from a microstructure of an object without attacking metal and or silicon dioxide films exposed to the composition used for removing the residues. Accordingly, said prior art hardly discusses the etching of TiN. Further, fluoride is also contained in the composition used in said prior art.
U.S. Pat. No. 6,136,711 describes a chemical mechanical polishing composition that is capable of polishing tungsten at high rates with minimal etching and/or corrosion. Said composition comprises a compound that is capable of etching tungsten, and comprises at least one inhibitor of tungsten etching. Specifically, a two-component solution is described with the two components being a film-forming agent which comprises a one-nitrogen atom-containing cyclic compound, and a silane compound, respectively.
In previous patents or study, the W-inhibitor, if present, also suppresses TiN etching rates. Thus, there is a need to find additives, which allow control over the relative etching rates of W and TiN, respectively. Moreover, if an additive binds, by either covalent or non-covalent bonds, to W and cannot be removed by subsequent rinsing, the resistance of the W-plug will not be acceptable and will affect reliability. Therefore, the solution should not only to protect the W surface, but also contain components that may be removed by a rinsing step with an appropriate solvent.